High-temperature fan



Oct. 7, 1947. I v c. NYGREN 2,423,765

HIGH-TEMPERATURE FAN,

Filed April 28, 1945 4 Sheets-Sheet 1 I INVENTOR. I Zzr/ A/Yf/Z Oct. 7,1947. Q'NYGREN I 2,428,765

HiGH-IEMPERATURE FAN 1 7 Filed April 28, 1945- 4 Sheets-Sheet 3 0a. 7,1947. c. NYGREN I 2, HIGHkTEMPERATU RE FAN Filed Apl il 28, 1945 4Shegts-Sheet 4 v fzwerzfok G 99 Patented Get. 7, 1947 UNITED STATESPATENT OFFICE Michiana Products Corporation,

Michigan City, bid, a corporation of Indiana Application April 28,1945., Serial No. 590,754

4 Claims.

Fans or blowers for handling gases at high temperatures such as are usedfor recirculation in heat treating furnaces are necessarily subjected toweakening temperatures and to varying extremes in expansion andcontraction, particularly when driven by water cooled shafts. Withtemperatures on the order of 1200 to 1800 degrees Fahrenheit in the gaspropelling outer parts of the fan and temperatures below 200 at theshaft. there is great tendency for the parts or the whole to get out ofdynamic balance or otherwise develop destructive stresses.

The principal object of this invention is to provide a well balancedstructure in which the parts are allowed freedom in expanding andcontracting individually and dynamic balance is continually maintained.

Generally speaking, this is accomplished by mounting the several bladesbetween circular. wheel-like side members with freedom to expand andcontract individually, axially, and radially.

A preferred embodiment of the invention for a 24-inch fan is shown inthe accompanying drawings, but these specific illustrations and thecorresponding description are used for the purpose of disclosure onlyand are not intended to exclude divers variations in the claims.

Figs. 1 and 2 are diagrammatic views of a double inlet fan and itsassociated parts in one form of installation;

Fig. 3 is a half longitudinal section through the axis of a hollow shaftand fan taken on the line 33 of Fig. 2, showing a specifically differentfan structure;

Fig. 4 is a side elevation of one of the blades;

Fig. 5 is an end view of the blades shown in Fig. 4 looking downwardlyfrom the upper end;

Fig. 6 is an edge view of the blade shown in Fig. 5 looking from eitherthe left or right;

Fig. 7 is a face view of one of the auxiliary hub members;

Fig. 8 is a longitudinal section through one of the auxiliary hubmembers;

Fig. 9 is a half section of the wheel shown in Fig. 3 taken at rightangles to the axis and a half end elevation:

Fig. 10 is an inside elevation of one of the side members;

Fig. 11 is a longitudinal section along the axis of one of the sidemembers; I

Fig. 12 is a half elevation of a single inlet fan corresponding to Fig.3;

Fig. 13 is an elevation of one of the blades used in that fan;

Fig. 14 is an edge elevation of Fig. 13 looking from the right in thatfigure;

Fig. 15 is an endview looking down on Fig. 13,

Fig. 16 is a face View of one of the auxiliary hub members; and

Fig. 17 is longitudinal section through that hub member on the axis ofrotation.

In Figs. 1 and 2, l0 indicates a conventional form of masonryinstallation for a fan or blower within which is a metal casing II for adouble inlet fan l2 mounted on a hollow shaft [3 journaled in bearings I4 and driven by a motor I5 through a V-belt drive I6. The inlet side ofthe water co ling unit is shown generally at I1, and

the return side is shown generally at l8.

Water cooling is ordinarily used in fan constructions for propellinghigh temperature fluids such as the gases recirculated in heat treatingfurnaces.

' The double inlet fan shown in Figs. 3-11 (Sheets 2 and 3) includes twowheel-like side pieces generally indicated by l9, twelve blades 20, andtwo auxiliary hub members generally indicated by 2|.

Each side member includes a hub member 22, a series of spokes or vanes23, and a ring-like rim 24, which forms the shroud of the fan.

On the inside of each shroud 24 there are twelve radial grooves 25 toreceive the edges of the blades 20 and hold them for driving the air butwith freedom to expand radially, axially, and circumferentially asoccasion may require,

Each auxiliary hub memebr 2| includes a hub portion 26 and a flange 21provided with twelve slots or notches 28 to receive and hold the innerend portions of the blades 20 for driving but with freedom to expand inall directions as occasion may require, and also freedom to moveradially and axially.

Each blade 20 is a generally rectangular flat plate with its innercorners cut away at 29 to provide inlets for the fan. At each side theblade is thickened to form a sort of rib 30 which ismachined'on theopposite faces to enter the grooves 25 with a push fit in the ordinaryconstruction. Adjacent to the inner end, each blade also has thickenedportions 30 machinedon opposite faces to be received within the notches28 with a like push fit, but with the freedom described.

This arrangement of blades, side members, and auxiliary hub membersprovides an appropriate assembly for wheel construction and leaves onlythe requirement for restraining the blades from outward movement undercentrifugal force individually or collectively. This may be taken careof by any sort of shoulder arrangement by which 7 24 with an inwardlydirected annular rib or flange 3| against which shoulders 32 at theouter corners of the blades come to rest under centrifugal force. Thisrestraint is all that is needed and leaves the blades, side members, andauxiliary hub members free to move relative to each other in expandingand contracting, and allows for the differences in expansion due to thevariations in temperature between the outer portions of the fan andthose inner portions under the strong influence of the water cooledshaft.

Alternative expedients for restraining the outward movement of bladesrelative to shrouds will be readily designed by engineers to suitindividual preference and the requirements of production. For example,in order to avoid having to machine the grooves 25 up to the ribs orflanges 3|, the lattermay be omitted, and each blade provided with ashoulder adjacent to the corners 29 for resting against the annularshoulders 34 and the side members ill, or both may be used.

The side members are here shown made in one piece and the auxiliary hubmembers in separate pieces, but this, of course, is a matter of choiceand design.

The side members and the auxiliary hub members are driven from the watercooled shaft through three keys 35 equally distributed around the shaftand fitted at their parallel sides only to key slots having parallelsides. freedom of expansion between the water cooled shaft and theheated hub members while maintaining a proper driving connection throughthe keys.

The left wheel member has its hub portion 22 resting against a shoulder38 on a shaft l3, while the right wheel member has its hub portion 22held assembled against the intermediate auxiliary hub portions by acollar 39 threaded on'the shaft 13 and locked by a washer 40 having atongue Al in a slot 42 in the shaft and a wing 43 bent into a slot 44 ina lock nut 45. The collar 39 will be set up, .wrenched tight, and thenbacked oif an amount determined by calculations or empirically to allowfor the necessary expansion, which will depend upon the alloys used andthe temperatures involved.

Figs. 12-17 (Sheet 4) show a similar fan constructionfor a single inletfan in which the parts correspond throughout to. those shown in Figs.3-11, except that the left wheel member H9 is a disk to close thecorresponding side of the fan and the blades I20 have the left side madeto correspond, as will appear from Figs. 12 and 13. Otherwise, it isdeemed sufficient to apply corresponding reference numerals to the parts'in Figs. 12-17.

Side member I9 is provided with anannular rib 41 in the area adjacent tothe shoulder 34 but on the other side of the shroud 24. This providesfor a special strength to resist the high tensile stresses due tocentrifugal forces and the natural tendency under those forces tostretch the shroud members. These ribs also make convenient grindingstock when the side members are being given the initial balance.

The side members, the blades, and the auxiliary hub members will in manycases have to be made of some kind of heat resisting alloy which will bedetermined largely by the tempera- This provides tures under which thefan is to be used modified by the corrosiveness of the atmosphere inwhich it is to be used. Some alloys providing'very high strength andresistance to high temperatures do not offer sufficient resistance tocorrosion for a long period of service, and some alloys especiallyadapted to resist certain types of corrosion are relatively weak ascompared With many of those which have high strength and high resistanceto temperatures. The choice of the alloy will determine the engineeringdesign and to some extent the clearances and tolerances, but thefollowing will serve as an example. The clearance between the blades andthe shroud members and hub members may be plus .002" minus .003". Whenthe grooves 25 are made with a milling cutter, they can be finishedclose up to the ribs 3| as shown. But the clearance between the ends ofthose grooves and the corresponding shoulders 32 on the blades may beconsiderable as compared with the other clearances, for centrifugalforce will hold the blades in their proper relation in use. The fitbetween the hub members and the shaft may be plus .002 minus .000". Thisis on the assumption, as preferred, that the shaft is made of carbonsteel and water cooled and the hub members are of a selected alloy.

According to the preferred procedure, the castings are machined andbalanced. Afterwards, they are annealed at a temperature above thatexpected to be encountered in service. Then, with finishing touches hereand there the fans are assembled and put through the final balancing.

I claim:

1. In a centrifugal fan, a plurality of blades in circular arrangementabout a common axis of rotation with their inner portions converginginwardly toward said axis and their outer portions diverging outwardlyfrom said axis, side pieces having hubs fixed against relative movementon a shaft and having shrouds grasping the outer portions of the bladesand interlocked therewith for normal rotation capable of appreciablerelative movement in expanding and contracting, flanges on theshroudslimiting the bodily outward movement of the blades, and a hub memberinterlocked with th inner portion of each blade with freedom forappreciable relative movement in expanding and contracting in adirection radial of the axis of rotation.

2. In a centrifugal fan, a plurality of blades in circular arrangementabout a common axis 7 of rotation with their inner portions converginginwardly toward said axis and their outer portions diverging outwardlyfrom said axis, side pieces having hubs fixed against relative movementon a shaft and having shrouds grasping the outer portions of the bladesand interlocked therewith for normal rotation capableof appreciablerelative movement in expanding and contracting, flanges on the shroudslimiting the bodily outward movement of the blades, and a hub memberhaving a slot receiving the inner ment on a shaft and having shroudsgrasping the outer portions of the blades and interlocked therewith fornormal rotation capable of appreciable relative movement in expandingand contracting, engaging flanges and shoulders on the shrouds andblades limiting the bodily outward movement of the blades, and a hubmember interlocked with the inner portion of each blade with freedom forappreciable relative movement in expanding and contracting in adirection radial of the axis of rotation.

4. In a centrifugal fan, a plurality of blades in circular arrangementabout a common axis of rotation with their inner portions converginginwardly toward said axis and their outer portions diverging outwardlyfrom said axis, side pieces having hubs fixed against relative movementon a shaft and having shrouds grasping the outer portions of the bladesand interlocked therewith for normal rotation capable of appreciablerelative movement in expanding and contracting, portions of the shroudsoverlapping portions of the blades to limit bodily outward movement ofthe blades, and a hub member concentric with the axis of rotationmounted between the side pieces and having a radial flange provided withan outwardly open radial slot receiving the inner end portion of eachblade for normal rotation with freedom for appreciable relative movementin expanding and contracting in a radial direction.

' CARL NYGREN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Williams Feb. 14, 1939 Number

